Apparatus for accurate powder metering

ABSTRACT

The invention concerns an apparatus ( 1 ) for accurate powder metering comprising: a container ( 2 ) or powder ( 3 ), including an adjustable opening ( 4 A,  4 B) through which the powder ( 3 ) is dispensed, said opening ( 4 A,  4 B) communicating directly with the container ( 2 ); means for adjusting ( 5 ) said opening ( 4 A,  4 B); means for controlling ( 6 ) the amount of powder ( 3 ) dispensed, in relation with said adjusting means, and means for vibrating and/or tapping ( 28 ) the container ( 2 ).

The present invention relates to an apparatus for accurately meteringout powder and to the method for implementing it and to its use.

In the chemical and pharmaceutical industry, it is often necessary toaccurately meter out reagents or products in powder form, particularlyfrom a combinatorial library. When tests are being conducted on a greatmany products in powder form, the successive metering operationsrepresent a particularly painstaking task to be performed by the staffinvolved.

Aside from the repetitive nature of the work, the staff involved have toinvest a considerable amount of time and attention to this type ofmetering.

These metering operations are all the more painstaking since the powdersthat are to be metered are generally of very different natures and haveflow indexes from a very wide range.

Furthermore, the metering difficulty is heightened by the fact that theamounts to be metered vary from a milligram to a hundredth of a gram,and at the same time require an accuracy in the order of one tenth of amilligram.

Finally, it is absolutely essential to avoid, on the one hand, the staffinvolved being contaminated with the products being metered and, on theother hand, cross-contamination or cross-pollution of the products, aproblem well known to those skilled in the art, as this makes thecontaminated samples unusable.

An initial approach sought to automate these metering operations to makethem less painstaking and more reliable, while at the same timemaintaining an acceptable metering accuracy.

Patent application FR 2 672 035 illustrates this type of device makingit possible to dispense defined masses of powders. This device consistsof a powder receptacle and of a metering stopper comprising a hopperfeeding an endless screw. This endless screw conveys powder to adispensing opening situated on the axis of rotation of the endless screwand on the side of the stopper.

Another device of the same type is described in patent application FR 2775 958. The principle of use of a stopper equipped with an endlessscrew with a dispensing opening at the end of the endless screw is,incidentally, already mentioned in a document as old as U.S. Pat. No.2,593,803.

These devices are adequate for delivering masses of powders from 5 toabout 8 mg, with an accuracy in the order of 1 mg.

By contrast, such devices are not suited to metering operations accurateto one tenth of a milligram.

Furthermore, they are not suited to metering quantities of the order ofone gram because the rate of metering is very soon limited by theendless screw dispensing system. The metering time then becomesexcessively long.

As far as metering out large quantities of powder is concerned, mentionmay be made of the device described in German utility model No. 89 14389 U in the name of Fink-Chemie GmbH. This device is equipped with aninlet feeding an endless screw with powder. This endless screw conveysthe powder toward a dispensing opening formed in the lower surface ofthe device.

It is, however, immediately evident that this type of device is notsuited to accurate metering of large amounts and small amounts ofpowders of varying types as is demanded in particular for combinatoriallibrary use. This device does, by contrast, seem to be suited to themetering out of large masses of certain types of powder where theaccuracy is of lesser importance. This utility model also makes nomention of any requirements on the accuracy of the metering.

Another device for accurately metering out powder, developed by theApplicant Company, has been described in patent applications FR 01 06090and PCT/FR02/01484, neither of which has yet been published.

These patent applications describe an improved metering stopper to befixed on a powder receptacle. This metering stopper comprises a hopperwhich feeds an endless screw. This endless screw transports the powderlaterally as far as an opening situated on the lower face of thestopper.

The improvement, which consists in placing the opening on the lower faceof the stopper, has made it possible to achieve mean metering accuraciesof the order of 0.1 mg, that is to say accuracies that are extremelysatisfactory for combinatorial library use.

However, disadvantages stem from the use of an endless screw mechanismin these metering devices.

Aside the problem of the slowness of the metering operation as mentionedhereinabove, this type of mechanism considerably restricts the extent towhich the metering apparatuses can be miniaturized. This is because anendless screw can be miniaturized only down to a limiting size belowwhich it can no longer fulfill its function of transporting the powderwith certain powders. As a consequence of this, it is difficult tominiaturize metering stoppers employing an endless screw below 2 cm formetering out certain powders.

Now, most pill-making equipment used in a combinatorial library setting,and to which the metering stoppers are fixed, are about 1.5 cm or lessin diameter.

Furthermore, the endless screw mechanism is no longer as effective whenit has to dispense powders with a flow index that is either very low,that is to say below 2, or very high, that is to say above 8. This isbecause, when the flow index is very low, the endless screw hasdifficulty in conveying the powder as far as the dispensing opening and,on the other hand, when the powder has a very high flow index, it slipsof its own accord along the screw thread without the endless screw beingactuated and being able to play its part in checking of the dispensing.

Another disadvantage is that, in the case of powders with a largeparticle size, the screw thread of the endless screw has a tendency tocrush the grains. Now, in certain applications, this tendency isabsolutely undesirable because it degrades the metered powder.

Finally, as chemical analysis methods are used on increasingly smallquantities of powder, the accuracy requirements are accordingly becomingever more severe.

Considering that there is a need for metering apparatus that addressesthese technical difficulties, the applicant company has developed theapparatus of the present invention for accurately metering out powder.

The invention is also aimed at a method for accurately metering outpowder employing the device of the invention and at the use of thisdevice for the accurate metering out of powder.

The metering device of the invention is particularly suited toaliquoting from a combinatorial library or for fractionation frombottles of reserve. It can be used with powders or small solids of verydiffering particle sizes and appearance, for example talc, lactose,cornstarch or sand. In this patent application and according to thedefinition given in the 3^(rd) edition of the DUVAL Dictionary ofChemistry [Dictionnaire de la Chimie 3^(éme) édition], the term “powder”denotes a finely divided solid.

The figures introduced hereinbelow illustrate particular embodiments ofthe invention. Their main purpose is to make the invention easier tounderstand and not to restrict it to only those embodiments that havebeen illustrated.

FIG. 1 is a schematic depiction of metering apparatus according to theinvention.

FIG. 2 is an exploded side view of a container according to theinvention.

FIG. 3 is a sectioned view of a container according to the invention.

FIG. 4 is a view of the underside of a container according to theinvention, the adjustable opening of which has been dismantled.

FIG. 5 is a view of the underside of a container according to theinvention.

FIG. 6 is another sectioned view of a container according to theinvention in a metering position.

FIGS. 7A, 8A, 9A and 10A are sectioned views of a container according tothe invention while it is in the process of operating.

FIGS. 7B, 8B, 9B and 10B are views of the underside of a containeraccording to the invention while it is in the process of operating.

FIG. 11 is a schematic perspective view of one particular embodiment ofthe container.

FIG. 12 is a sectioned view of one particular embodiment of thecontainer according to the invention, comprising a stirrer.

FIG. 13 is a perspective view of the stirrer depicted in FIG. 12.

FIG. 14 is a perspective and sectioned view of one particular embodimentof the dispensing opening of the container according to the invention.

The apparatus (1) for accurately metering out powder, that is thesubject of the invention, comprises:

-   -   a container (2) of powder (3), comprising an adjustable opening        (4A, 4B) through which the powder (3) is dispensed, said opening        (4A, 4B) being in direct communication with the container (2);    -   adjusting means (5) for adjusting said opening (4A, 4B);    -   a checking means (6) for checking the amount of powder (3)        dispensed, in relation with said adjusting means (5); and    -   a vibrating (27) and/or tapping (28) means for vibrating or        tapping the container (2).

The Applicant Company has discovered that, surprisingly, the vibratingand/or tapping means are, in their own right, means for substantiallyimproving the accuracy with which the powders can be metered out. Whathappens is that vibrating and/or tapping the container (2) allows veryfine metering of the powders, this being finer than is permitted byvarying the opening (4A, 4B) alone.

As a result of this, the apparatus (1) allows powders to be dispensedwith an accuracy of 100 μg or better, preferably with an accuracy of 50μg or better, and more preferably still with an accuracy of 10 μg orbetter. That means that with certain powders, the apparatus (1) iscapable of dispensing with an accuracy of 2 μg or better, and even withan accuracy as good as 1 μg. With certain powders, the apparatus (1) cantherefore meter to an accuracy of one grain of powder.

In terms of mean accuracy, the apparatus (1) is able to dispense powderswith a mean accuracy of 0.5 mg or better, preferably with a meanaccuracy of 0.2 mg or better, and more preferably still with a meanaccuracy of 0.1 mg or better. The mean accuracy is the accuracy obtainedfor most weighings, that is to say for at least 50% of the weighingsperformed, preferably at least 75% and more preferably still at least85% of the weighings. The maximum figure of 100% of the weighings couldeven be achieved in some cases.

Better accuracy is to be understood as being finer or superior accuracy,so that the metering is more precise.

Furthermore, the apparatus (1) according to the invention makes itpossible to meter out powders having a flow index lying within a verybroad range. Powders having a flow index of 2 or lower or of 8 orhigher, preferably powders having a flow index below 1 or above 9, oreven of 10 or higher, can be metered out with the abovementionedaccuracies.

The flow index is defined as the greater or lesser aptitude of thepowder to being metered. This aptitude is influenced by various factorssuch as: viscosity, electrostatic charges borne, or alternatively theparticle size or moisture content and capillary forces. This flow indexis generally defined on a scale from 0 to over 10. Powders with an indexfrom 0 to 2 are said to be highly cohesive, those from 2 to 4 are saidto be cohesive, those from 4 to 10 are said to be average and those withan index higher than 10 are said to be free flowing. The flow index mayfor example be determined by the JENIKE test, which is a test well knownto those skilled in the art.

The document entitled “MESSSIGNALVERARBEITUNG UND REGELUNG IN ABFULL-UND ABSACKANLAGEN”, WAGEN UND DOSIEREN, VERLAGSGESELLSCHAFT KEPPLER,MAINZ, DE, VOL. 19, No. 3, pages 92-96 XP000003020 by PANDIT, relates tothe processing of the measurement signal and the adjustments for fillingand bagging devices. That document incidentally describes an apparatusconsisting of a container provided with a variable opening containingpowder to be dispensed, means for adjusting the opening and a balancefor weighing out the powder. That document does not, by contrast, seemto cover accurate metering. It should also be emphasized that thedocument does not quote any metering accuracy.

Furthermore, unlike the invention, that document does not describe ameans for vibrating and/or for tapping the container.

U.S. Pat. No. 5,738,153 also describes a device for metering out powdercomprising a valve-controlled variable opening. By contrast, thatdocument does not describe a means for vibrating and/or for tapping thecontainer either.

As a result, none of the metering devices described in the prior art isable to achieve the metering accuracies achieved by the device accordingto the invention.

Furthermore, because the apparatus (1) according to the invention has noendless screw, it can be miniaturized down to dimensions smaller than0.2 cm, or even dimensions of 1 cm or smaller.

In addition, the absence of an endless screw allows faster dispensing,without grinding the grains of powder to be metered. By way of example,metering 2 g of powder, for example cornstarch, has been achieved inunder 20 seconds, this being with the accuracies mentioned hereinabove.

The detailed description which follows, describing the apparatus (1),the means it comprises and their interaction, will allow for a betterunderstanding of the invention.

The apparatus (1) according to the invention comprises a container (2)of powder (3).

This container can be in one or more parts.

In one particular embodiment, the container (2) is in two parts, areceptacle part (8) and a stopper part (9). In this case, the receptacle(8) and stopper (9) parts can be fixed together by any means known tothose skilled in the art, for example by screw-fastening or clipping. Inorder to seal the connection between the receptacle (8) and the stopper(9), a gasket (10) may be provided.

A hopper (14) may also be arranged inside the container (2) to guide thepowder (3) as far as the adjustable opening (4A, 4B) and thus assistwith feeding said opening.

The container (2) may be of any size or shape, particularly in the shapeof a cone, of circular or non-circular cross section, delimited by awall, a first and a second end face. These end faces may beperpendicular to the axis of the cone or may not. The container (2) maybe made of any material that is thermally stable under the conditions ofuse and storage and chemically inert with respect to the powders thatare to be metered out. This may in particular be a polymer material suchas polyethylene, polypropylene, fluorinated polymers, for examplepolytetrafluoroethylene (Teflon™). In the case of a container (2) madein two parts, each of the receptacle (8) and stopper (9) may be molded.

The container (2) may also be covered by a hood (7) when it is notoperating, particularly for storage. This hood (7) preserves the powder(3) against the air.

The container (2) is directly connected or communicated with theadjustable opening (4A, 4B), that is to say communicates or connects insuch a way that the powder (3) can be conveyed from the container (2)toward the adjustable opening (4A, 4B) under the simple effect ofgravity, particularly without being conveyed by a mechanical element,for example an endless screw.

It is also possible to anticipate various types of adjustable opening,particularly plug-valve (4A, 4B) or slide-valve (4A, 4C) controlled.This adjustable opening (4A, 4B) or (4A, 4C) will preferably beadjustable to the extent of being completely closed off.

The plug valve (4B) may be of the cylindrical valve type, preferably ofthe tapered cylindrical valve type for sealing reasons.

The adjustable opening (4A, 4B) is adjusted by adjusting means (5) whichare connected to a dispensing checking means (6).

The adjusting means (5) are capable of adjusting the size of the openingso as to allow the metering of the powder (3) to be more or less rapidand more or less accurate. Specifically, the smaller the adjustableopening (4A, 4B) the lower the flow rate of dispensed powder (3) and thegreater the accuracy. Conversely, the larger the adjustable opening (4A,4B), the higher the flow rate of dispensed powder (3) and the lower theaccuracy.

Appropriate adjusting means (5) are, for example, a motor connected witha transmission element (11) driving the closure or opening of theadjustable opening (4A, 4B). This adjustable opening (4A, 4B) generallycomprises two parts: an actual opening (4A) proper and a mechanism (4B)for opening and closing the opening. A great many shapes can beanticipated for the opening (4A), for example circular, square,diamond-shaped or alternatively triangular. The preferred shape of theadjustable opening (4A, 4B) is, however, the shape of a triangle.

In the case of a plug valve opening (4A, 4B), the transmission element(11) may be a rod, connected to a motor, the cruciform male end of whichcollaborates with a cruciform female notch at the end, on the axis ofthe plug (4B).

Metering is checked by a checking means (6). This checking means maycomprise any means suitable for determining the amount of powder (3)dispensed. This checking means (6) may for example by an optical means,such as a laser, or a device measuring the volume of the powder. Thechecking means (6) is preferably a weighing means able to weigh theamount of powder already dispensed through the adjustable opening (4A,4B). The remainder of this application will mainly discuss weighingmeans without excluding any other checking means.

An appropriate weighing means (6) is, for example, a balance having aweighing accuracy of 0.1 mg or better.

The checking means (6) is connected to the adjusting means (5). Thisconnection is preferably by way of an electronic relationship.

The checking means (6) measures the amount of powder (3) alreadydispensed through the adjustable opening (4A, 4B) and returns themeasurement value to the adjusting means (5) which, as a function of theweighed value returned, will adjust the metering by opening theadjustable opening (4A, 4B) further or closing it.

The adjusting means (5) may comprise a computer equipped with software.The software may be capable of processing the values of the measurementsreturned by the checking means (6). This software may also control theadjusting means (5) as a function of the checking measurements suppliedby the checking means (6). The adjusting means (5) may also comprise amotor connected to a transmission element (11) actuating the opening orclosure of the adjustable opening (4A, 4B).

The adjusting means (5) may furthermore be parameterized as a functionof the nature of the powder to be dispensed. What happens is that, ifthe powder has a high flow index, it will have a tendency to flow veryquickly through the adjustable opening (4A, 4B). The software maytherefore be parameterized such that the adjustable opening (4A, 4B) isopen only a very small amount when metering such powders.

During the metering, the container (2) is tapped and/or vibrated.

The tapping and/or vibrating has/have two main effects.

The first effect is to make it easier to dispense the powder byunclogging the powder or eliminating the roof or chimney effects thatoccur in the container (2). That makes it easier to feed the adjustableopening (4A, 4B).

The second effect is that of substantially improving the accuracy withwhich the powders are metered. This is because vibrating and/or tappingcauses the powder to move in the container (2) and gradually conveys itas far as the dispensing opening (4A, 4B). Vibrating and/or tappingtherefore represent a very fine way of feeding the opening (4A, 4B) andtherefore of metering.

In this case, the device according to the invention will advantageouslycomprise a device encouraging the dispensing of powder, particularly bytapping using, for example, a movable and retractable finger which canstrike the container (2), for example 4 times per second, and/or byvibrating using, in particular, a fork in which the device is held.

The person skilled in the art will recognize that numerous types ofdevice are suitable by way of means for vibrating and/or tapping thecontainer (2).

Optional means encouraging dispensing may also be fitted to theapparatus (1) according to the invention.

In the case of powders that do not flow very well or that generate roofeffects and in order to make it easier for the powder to drop downtoward the opening, the inside of the container (2) may be equipped withstirrers (12) which assist with feeding the adjustable opening (4A, 4B).The purpose of these stirrers is to disturb the roof effects by stirringup the powder or alternatively by forcing product toward the adjustableopening (4A, 4B). Such stirrers (12) may, for example, be a rotary drillfitted with paddles.

In one particular embodiment of the apparatus (1) according to theinvention, said stirrer (12) comprises a rotary drill arranged along anaxis passing through the opening (4A, 4C) and more or less normalthereto, said drill comprising:

-   -   a first end situated near the opening (4A, 4C), said first end        having a screw thread able to convey the powder toward the        opening (4A, 4B),    -   a second end at the opposite end to the first end, said second        end being fixed to a rotor,    -   paddles fixed to the drill and projecting radially from the axis        of rotation.

According to another embodiment of the apparatus according to theinvention, the stirrer (12) may be arranged along an axis passingthrough the opening (4A, 4B), said stirrer (12) comprising:

-   -   a first end (12A) arranged near the mid-plane of the opening        (4A, 4B), and    -   a second end (12B) at the opposite end to the first end (12A)        and which is connected to a device transmitting to the stirrer        (12) a back-and-forth movement along said axis passing through        the opening (4A, 4B), and possibly a rotary movement about said        axis passing through the opening (4A, 4B).

The stirrer (12) may be connected reversibly to the device transmittinga back-and-forth and rotational movement to it. The stirrer (12) may,for example, be connected to it by screw-fastening, clipping or anyother suitable means known to those skilled in the art.

According to a preferred embodiment of the apparatus (1) according tothe invention, the stirrer (12) is a rod (16).

According to another preferred embodiment of the apparatus (1) accordingto the invention, the first end (12A) of said stirrer (12) comprises arod (16) and the second end (12B) of said stirrer (12) comprises a leaf(15) bent back on itself to form a loop that is elongate along said axispassing through the opening (4A, 4B), said leaf (15) comprising fins(15A) which project from the interior surface of the bent-over leaf (15)toward said axis.

According to one embodiment of the apparatus (1) according to theinvention, the device transmitting a back-and-forth movement to thestirrer comprises:

-   -   a transmission means (17) connected to the second end (12B) of        the stirrer (12),    -   a pushing means (21),    -   a pulling means (18),        said pushing means (21) transmitting a translational movement to        said transmission means (17) in a first direction along the axis        of said transmission means (17) and said pulling means (18)        transmitting a translational movement to said transmission means        (17) in the opposite direction to the first direction.

The device transmitting a rotary movement to the stirrer may comprise atransmission means (17) connected to the second end (12B) of the stirrer(12), said transmission means (17) comprising driving gearing (22) whichis driven by drive gearing (23) fixed to a motor (24).

Furthermore, in one particularly preferred embodiment of the apparatusaccording to the invention, in the stirrer (12):

-   -   the first end (12A) of said stirrer (12) comprises a rod (16)        and the second end (12B) of said stirrer (12) comprises a leaf        (15) bent back on itself to form a loop that is elongate along        said axis passing through the opening (4A, 4B), said leaf (15)        comprising fins (15A) which project from the interior surface of        the bent-over leaf (15) toward said axis,    -   the device transmitting a back-and-forth movement to the stirrer        comprises a transmission means (17) connected to the second end        (12B) of the stirrer (12), a pushing means (21), a pulling means        (18), said pushing means (21) transmitting a translational        movement to said transmission means (17) in a first direction        along the axis of said transmission means (17) and said pulling        means (18) transmitting a translational movement to said        transmission means (17) in the opposite direction to the first        direction,    -   the device transmitting a rotary movement to the stirrer (12)        comprises a transmission means (17) connected to the second end        (12B) of the stirrer (12), said transmission means (17)        comprising driving gearing (22) which is driven by drive gearing        (23) fixed to a motor (24).

The transmission means may, for example, be a bar, shaft or rotor.

The pushing means may, for example, be a pneumatic or hydraulic ram.

The pulling means may, in particular, be a spring or a second pneumaticor hydraulic ram.

The person skilled in the art will recognize that numerous types ofmaterial can be used for the stirrer (12). However, the stirrer (12)will preferably be made of foil.

Furthermore, in the apparatus (1) according to the invention, thetapping means and/or the stirrer (12) may be controlled by software as afunction of checking measurements supplied by the checking means (6) andpossibly as a function of characteristics of the powder (3).

It is also possible to anticipate equipping the container (2) with ascraper (13) for scraping the powder (3) that lies at the bottom of thecontainer (2) to make it easier to dispense when the container (2) is inoperation. This scraper (13) may, for example, be a curved blade,preferably mounted to pivot on a vertical axis of the container (2).This scraper (13) may also be a rotary brush. This rotary brush may inparticular be positioned and set in rotation on an axis parallel to theplane defined by the adjustable opening (4A, 4B).

The device according to the invention may also be coupled to one or moreanti-electrostatic devices that generate an electric field encouragingthe distribution of the powder. Without being bound by any particulartheory, the Applicant Company believes that the powders to be meteredare naturally charged or that the friction between the grains of theproduct to be metered and the elements of the device generates chargedspecies. The charges give rise to forces causing, in particular, thegrains to clump together or causing the grains to be magnetized oncontact with the elements of the apparatus (1). As a preference, theapparatus (1) according to the invention is thus equipped with at leastone anti-electrostatic device placed on the container (2) at the exit ofthe adjustable opening (4A, 4B) and generating an electric field thatallows the movement of the particles to be routed. In order to cover theentire dispensing opening, use will preferably be made of twoanti-electrostatic devices. An anti-electrostatic device may be a spikeionizing probe generating an electrical field of 4 kV for example.

A method for metering out powder employing the apparatus (1) accordingto the invention may comprise one or more of the following steps:

-   -   bringing the container (2) into the metering position,    -   using the adjusting means (5) to open the adjustable opening        (4A, 4B),    -   vibrating and/or tapping the container (2),    -   using the checking means (6) to measure the amount of powder (3)        dispensed,    -   using the adjusting means (5) to open or close the adjustable        opening (4A, 4B) as a function of the measurement returned by        the checking means (6),    -   adjusting the means that vibrate and/or tap the container (2) as        a function of the measurement returned by the checking means        (6).

When metering is over, the container (2) is possibly capped with a hood(7) designed for this purpose.

FIG. 1 is an overall view of one embodiment of the apparatus (1) in thecourse of operation. The container (2) which contains the powder (3) isin the metering position as depicted in section. This container (2) isconnected to adjusting means (5) for adjusting the adjustable opening(4A, 4B). The powder is metered through this adjustable opening (4A, 4B)into pill-making equipment arranged under the container (2). Thispill-making equipment is placed on the checking means (6) which in thisinstance is depicted in the form of a precision balance. The checkingmeans (6) is connected with the adjusting means (5). In this figure, thecontainer (2) is held via vibrating means (27) for vibrating thecontainer (2). This vibrating and/or tapping means is a holding fork(27, 28) in this figure. The vibrating and/or tapping means in thisinstance is combined, that is to say one and the same element.

FIG. 2 is an exploded view of an embodiment of a container (2) made intwo parts and with a plug valve opening (4A, 4B). The hood (7) has beenremoved from the stopper (9). The plug valve (4B) will sit in thehousing of the stopper (9) and collaborates with the transmissionelement (11). The stopper (9) has been unscrewed from the receptacle(8).

FIG. 3 is a sectioned view of a container (2) made in two parts. In thisfigure, the container (2) is depicted with its adjustable opening (4A,4B) at the top, that is to say when it is not in operation. Furthermore,the hood (7) covers the stopper (9). The plug valve (4B) is depictedalong an axis retreating into and perpendicular to the page. It ispossible to make out the cruciform female notch that collaborates withthe cruciform male end of the transmission element (11).

FIG. 4 is an exploded view of the dispensing face of the stopper (9)depicted in FIG. 2. The plug valve opening (4A, 4B) comprises atriangular opening (4A) and a plug (4B) out of its housing in thestopper (9). The transmission element (11) has been withdrawn from theplug (4B). FIG. 14 is another view, in perspective and in section, ofthe triangular opening (4A).

FIG. 5 is a view of the dispensing face of the stopper (9) once fitted.In this view, the plug valve (4B), which cannot be seen, is placed inthe stopper (9) and collaborates with the opening (4A). The transmissionelement (11) is depicted withdrawn from the cruciform notch in the plug(4B).

FIG. 6 is a view in section of the container (2) ready to operate. Thestopper (9) is screwed onto the receptacle (8) around the gasket (10).The hopper (14) feeds the adjustable opening (4A, 4B). A tapping means(28) depicted in the form of a retractable finger (28) is arranged onthe side of the container (2) to allow the container (2) to be tapped.

FIGS. 7A, 8A, 9A and 10A and 7B, 8B, 9B and 10B illustrate the operationof a container (2) during the metering operation.

FIGS. 7A, 8A, 9A and 10A are sectioned views of a container (2) and areto be placed in parallel with FIGS. 7B, 8B, 9B and 10B which are viewsof the lower surface of the same container (2).

Before the start of metering, the adjustable opening (4A) is completelyclosed off in FIGS. 7A and 7B.

At the start of metering (FIGS. 8A and 8B), the plug (4B) is turned onits axis and slightly opens the adjustable opening (4A) which dispensesthe powder (3) at a very low flow rate.

In FIGS. 9A and 9B, the plug (4B) continues to turn and opens theadjustable opening (4A) wider. The flow rate of powder (3) is thereforehigher.

Finally, in FIGS. 10A and 10B, the plug (4B) fully opens the adjustableopening (4A) and the flow rate of powder (3) dispensed is then at itsmaximum.

FIG. 11 is a perspective view of another embodiment of the container (2)according to the invention. In this embodiment, the container (2)comprises a stirrer (12) in the form of a rotary drill equipped withblades. The rotary drill advantageously also bears a scraper (13) whichis a curved blade. The adjustable opening (4A, 4C) here comprises anopening (4A) and a valve slide (4C).

FIG. 12 is a sectioned view of one embodiment of a container (2)comprising an opening with a tapered cylindrical plug (4A, 4B) and astirrer (12).

FIG. 13 is a perspective view of the stirrer (12) depicted in FIG. 12.

In these figures, the stirrer (12) is arranged along an axis passingthrough the opening (4A, 4B). The stirrer has a first end (12A) which isarranged near the mid-plane of the opening (4A, 4B) and a second end(12B) at the opposite end to the first end (12A). The first end (12A) ofsaid stirrer (12) is a rod (16) and the second end (12B) of said stirrer(12) is a leaf (15) bent back on itself to form a loop that is elongatealong said axis passing through the opening (4A, 4B). Said leaf (15)comprises fins (15A) which project from the interior surface of thebent-over leaf (15) toward said axis.

This second end is connected to a device transmitting to the stirrer(12) a back-and-forth movement along said axis passing through theopening (4A, 4B) and a rotational movement about said axis passingthrough the opening (4A, 4B). The device transmitting a back-and-forthmovement to the stirrer comprises a transmission means (17) which isconnected to the second end (12B) of the stirrer (12), a pushing means(21) and a pulling means (18).

In this instance, the pushing means (21) is a ram and said pullingelement is a spring (18), arranged inside a spring cage (20).

The ram (18) transmits a translational movement to said transmissionmeans (17) via the plate (19) in a first direction along the axis ofsaid transmission means (17). The transmission means (17) thereforetransmits a translational movement in a first direction to the stirrer(12). In its translational movement, the transmission means (17) (inthis instance a bar) drives the gearing (22) fixed thereto. The gearing(22) therefore moves with respect to the gearing (23).

Through its translational movement, the ram (18) compresses the spring(18) from its rest position into a compressed position. When the actionof the ram (18) is halted and the ram no longer applies force to thespring (18), the spring (18) returns to its rest position, transmittinga translational movement to said transmission means (17) in the oppositedirection to the direction of travel transmitted by the ram (21). Byrepeating the action of the ram (21) and of the spring (18) aback-and-forth movement of the stirrer (12) and of the rod (16) iscreated.

The rod (16) will, as a result, move translationally along the axis ofthe stirrer (12) in the opening (4A, 4B). This has the effect of feedingor cramming the opening (4A, 4B), something which is particularlyadvantageous in the case of highly cohesive powders which are difficultto meter. The length of the rod (16) may be sufficient to pass themid-plane of the opening (4A, 4B) and even protrude from the container(2) by a few millimeters.

The transmission means (17) further comprises driving gearing (22) whichis driven by drive gearing (23) fixed to a motor (24). In this way, thestirrer (12) has not only a translational movement along its axis butalso a rotational movement about this same axis.

A ball bearing assembly (25) comprising bearings (26) guides thetransmission means (17) in its translational and rotational movement.

The apparatus (1) according to the invention is particularly suited tobeing used in a step of a method for the accurate metering out ofpowder. The apparatus (1) is also very suited to use in the accuratemetering out of powder.

1-24. (canceled)
 25. An apparatus for accurately metering out powder,comprising: a container of powder, comprising an adjustable openingthrough which the powder is dispensed, said opening being in directcommunication with the container; adjusting means for adjusting saidopening; and a checking means for checking the amount of powderdispensed, in relation with said adjusting means; and a vibrating and/ortapping means for vibrating or tapping the container, wherein thecontainer further comprises a stirrer situated within the interiorvolume of said container, and wherein said stirrer is arranged along anaxis passing through the opening, said stirrer comprising: a first endarranged near the mid-plane of the opening, and a second end at theopposite end to the first end and which is connected to a devicetransmitting to the stirrer a back-and-forth movement along said axispassing through the opening, and possibly a rotary movement about saidaxis passing through the opening.
 26. The apparatus as claimed in claim25, which is capable to dispense powders with an accuracy of 100 μg orbetter, preferably with an accuracy of 50 μg or better, and morepreferably still with an accuracy of 10 μg or better.
 27. The apparatusas claimed in claim 25, which is capable to dispense powders with a meanaccuracy of 0.5 mg or better, preferably with a mean accuracy of 0.2 mgor better, and more preferably still with a mean accuracy of 0.1 mg orbetter.
 28. The apparatus as claimed in claim 25, in which the openingis adjustable to the extent of being completely closed off.
 29. Theapparatus as claimed in claim 25, in which the opening is in the shapeof a triangle.
 30. The apparatus as claimed in any claim 25, in whichthe opening is chosen from an opening with a plug valve or an openingwith a slide valve.
 31. The apparatus as claimed in claim 25, in whichthe container comprises a receptacle part and a stopper part.
 32. Theapparatus as claimed in claim 25, in which the container comprises ahopper feeding the opening.
 33. The apparatus as claimed in claim 25, inwhich the adjusting means are controlled by software as a function ofchecking measurements supplied by the checking means.
 34. The apparatusas claimed in claim 25, in which the adjusting means comprise a motorconnected to a transmission element actuating the opening or closure ofthe adjustable opening.
 35. The apparatus as claimed in claim 25, inwhich the checking means is a balance having a weighing accuracy of 0.1mg or better.
 36. The apparatus as claimed in claim 25, in which themeans for tapping the container is a retractable finger that strikes theoutside of the container.
 37. The apparatus as claimed in claim 25, inwhich the stirrer is a rod.
 38. The apparatus as claimed in in claim 25,in which the first end of said stirrer comprises a rod and the secondend of said stirrer comprises a leaf bent back on itself to form a loopthat is elongate along said axis passing through the opening, said leafcomprising fins which project from the interior surface of the bent-overleaf toward said axis.
 39. The apparatus as claimed in claim 25, inwhich the device transmitting a back-and-forth movement to the stirrercomprises: a transmission means connected to the second end of thestirrer, a pushing means, a pulling means, said pushing meanstransmitting a translational movement to said transmission means in afirst direction along the axis of said transmission means and saidpulling means transmitting a translational movement to said transmissionmeans in the opposite direction to the first direction.
 40. Theapparatus as claimed in claim 25, in which the device transmitting arotary movement to the stirrer comprises a transmission means connectedto the second end of the stirrer, said transmission means comprisingdriving gearing which is driven by drive gearing fixed to a motor 41.The apparatus (1) as claimed in claim 25, in which: the first end ofsaid stirrer comprises a rod and the second end of said stirrercomprises a leaf bent back on itself to form a loop that is elongatealong said axis passing through the opening, said leaf comprising fins(which project from the interior surface of the bent-over leaf towardsaid axis, the device transmitting a back-and-forth movement to thestirrer comprises a transmission means connected to the second end ofthe stirrer, a pushing means, a pulling means, said pushing meanstransmitting a translational movement to said transmission means in afirst direction along the axis of said transmission means and saidpulling means transmitting a translational movement to said transmissionmeans in the opposite direction to the first direction, the devicetransmitting a rotary movement to the stirrer comprises a transmissionmeans connected to the second end of the stirrer, said transmissionmeans comprising driving gearing which is driven by drive gearing fixedto a motor.
 42. The apparatus as claimed in claim 25, in which thetapping means and/or the stirrer are controlled by software as afunction of checking measurements supplied by the checking means andpossibly as a function of characteristics of the powder.
 43. Theapparatus as claimed in claim 25, in which the container furthercomprises a scraper, preferably a curved blade or a rotary brush.
 44. Aprocess for accurately metering out powders employing the apparatus asclaimed in claim 25, comprising one or more of the following steps:bringing the container into the metering position, using the adjustingmeans to open the adjustable opening, possibly vibrating or tapping thecontainer, using the checking means to measure the amount of powderdispensed, using the adjusting means to open or close the adjustableopening as a function of the measurement returned by the checking means,adjusting the means that vibrate and/or tap the container as a functionof the measurement returned by the checking means.